Originally Posted by
Parashooter
1/4" back of bolt-closed is near the point where the bolt head crosses the dismount notch on the No4 Mk1* guide rail. It's possible the rail is damaged and/or the bolt head's rail groove is not chamfered. With a cartridge present, the extractor spring urges the bolt head toward the rail, possibly explaining the occurrence of the malfunction only when extracting a cartridge. Try pressing the bolt head down and to the left (away from the rail) during extraction. If the problem is alleviated, you may have identified the source.